Catalyst for selective hydrogenation of nitro groups of halonitro aromatic compounds

ABSTRACT

A supported catalyst for hydrogenating nitro groups of halonitro compounds manufactured from a support, a solvent, and one or more types of organometallic complexes. The organometallic complexes have the formula:  
                 
 
wherein, R 1 -R 6  are independently an R, OR, OC(═O)R, halogen, or combination thereof, where R stands for an alkyl or aryl group; Y 1 -Y 4  are independently an O, S, N, or P atom; and M is a metal atom. The supported catalysts show much higher selectivity and activity when used to hydrogenate nitro groups on halonitro aromatic compounds than catalyst currently being used for such hydrogenation.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a division of copending U.S. application Ser. No.11/216,407, filed Aug. 31, 2005, the disclosure of which is incorporatedherein in its entirety.

BACKGROUND OF THE INVENTION

1. The Field of the Invention

The present invention relates to catalysts and methods for selectivehydrogenation of nitro groups of halonitro aromatic compounds.

2. The Relevant Technology

Aromatic amines are important intermediates in the manufacture of dyes,drugs, herbicides and pesticides. It is known that halonitro aromaticcompounds may be reduced to amino aromatic compounds in good yields inthe presence of noble metal catalysts and hydrogen (i.e., in ahydrogenation process).

Substantial efforts have been exerted to find conditions in which nitrogroups are hydrogenated to form amines without producing undesired sidereactions. However, traditional processes for hydrogenating nitro groupsoften yield undesirable side reactions. For instance, nitro compoundshave the tendency to form azo compounds during hydrogenation. Forexample, the hydrogenation of 2-halo-nitrobenzene can result information of substantial amounts of

These and other byproducts are often harmful to the environment and aretypically expensive to dispose of.

Many important nitro aromatic compounds also include otherhydrogenatable groups such as halogens. Dehalogenation has been found tooccur when using catalysts made from palladium, platinum, rhodium,nickel and copper chromite. The halogen or other hydrogenatable group isoften an important substituent for subsequent reactions or for the finalproduct. Thus, dehalogenation of halonitro aromatic compounds oftenproduces unwanted byproducts. To avoid these undesired byproducts, thenitro group needs to be selectively hydrogenated.

Selective hydrogenation reactions are influenced by many factors.Traditional hydrogenation processes have focused on optimizingconditions by adding catalytic activators, adjusting reactiontemperature, adjusting reaction pressure, solvent agitation, and/ormodifying other conditions.

BRIEF SUMMARY OF THE INVENTION

The present invention provides various supported catalysts comprised oforganometallic compounds dispersed on a solid support. The supportedcatalysts show much higher selectivity and activity when used tohydrogenate nitro groups on halonitro aromatic compounds compared tocatalysts currently used for such hydrogenation reactions.

Supported catalysts according to the invention include a metal centerthat is coordinated with an acetylacetonate backbone ligand structure.The organometallic complexes have a structure according the followingformula:

wherein,

-   -   R₁-R₆ comprise, independent of one another, one or more of an R,        OR, OC(═O)R, or halide, wherein R stands for an alkyl, an aryl,        or a hydrogen;    -   Y₁-Y₄ are independently an O, S, N, or P atom; and    -   M is a metal atom.

In a preferred embodiment, the metal atom is selected from the groupcomprising palladium, platinum, ruthenium, and rhodium. These metalshave been found to be particularly useful in combination with theacetylacetonate based structure for selectively hydrogenating halonitrocompounds.

The organometallic complexes of the present invention allow thecatalytically active metal centers to be highly dispersed on thesupport. The high dispersion and separation between active metal centersis believed to contribute to the selectivity of the catalyst. Thedispersion and/or steric hindrances provide fewer opportunities forpartially reduced nitro species to react together to form undesiredcoupling compounds, such as

Reducing the formation of undesired coupling compounds results in higheryields of the desired haloamino aromatic compound. It may, in somecases, eliminate the need to distill the haloamino compound.

The bulkiness of the acetylacetonate based ligands provides spacingbetween the metal centers to facilitate dispersion. The high dispersionand separation between active metal centers is believed to contribute tothe selectivity of the catalyst when used for hydrogenation of nitrogroups. Because the active centers are spaced apart, there is lessopportunity for partially reduced nitro species to react together toform undesired coupling compounds.

The present invention also includes methods for manufacturing the highlyselective catalysts of the present invention. In a preferred embodiment,the method includes dispersing a solution or suspension of anorganometallic complex on a solid support and reducing the metal atomsto activate the catalyst. The activation step is either performedwithout oxygen, or where oxygen is present, the catalyst is treated attemperatures below about 100° C. Preparing the catalyst according tosteps of the present invention produces a catalyst with higherselectivity for hydrogenating nitro groups.

It is believed that the higher selectivity of the catalysts of thepresent invention is achieved through one or more of the followingfeatures: good dispersion of the metal on the support, separation ofcatalysts atoms due to the steric hindrances of the organic ligands,separation of catalysts atoms due to bonding with the support, and/orreduced agglomeration during manufacture of the catalyst.

These and other benefits, aspects and features of the present inventionwill become more fully apparent from the following description andappended claims as set forth hereinafter.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS I. Method of MakingCatalyst

In general, manufacturing supported catalysts of the present inventionincludes (i) selecting an organometallic complex that can provide theproper spacing between metal atoms, (ii) selecting a support material,(iii) dispersing the organometallic complex on the support material toform an intermediate supported catalyst, and (iv) activating theintermediate supported catalyst.

A. Organometallic Complexes

The organometallic complexes are compounds that have catalytic metalcenters, or that upon further processing of the complex, the metalcenter can perform a catalytic function. The supported catalysts includea metal center that is coordinated with an acetylacetonate backboneligand structure. In a preferred embodiment the organometallic complexeshave a structure according the following formula:

wherein,

-   -   R₁-R₆ comprise, independent of one another, one or more of an R,        OR, OC(═O)R, or halide, wherein R stands for an alkyl, an aryl,        or a hydrogen;    -   Y₁-Y₄ are independently an O, S, N, or P atom; and    -   M is a metal atom.

The metal atom is selected according to its ability to catalyzehydrogenation of nitro groups of halonitro aromatic compounds. In apreferred embodiment, the metal atom is a palladium, platinum,ruthenium, or rhodium atom. These metals can be complexed withacetylacetonate and its derivatives and are particularly useful forselectively hydrogenating nitro groups.

In a preferred embodiment the metal atoms and the acetylacetonatestructure are selected to have a planar structure. If the organometalliccomplex is planar, the π electrons in the acetylacetonate structure canbond better with the support material.

The organometallic complexes of the present invention allow thecatalytic metal centers to be highly dispersed on the support. Thebulkiness of the acetylacetonate based ligand structure provides spacingbetween the metal centers to facilitate dispersion.

Obtaining a desired separation between the metal centers can beaccomplished through the selection of R₁-R₆. In an exemplary embodiment,R₁-R₄ are CH₃ groups and R₅ and R₆ are H groups (i.e., the metal iscomplexed with two acetylacetonate ligands). In an alternativeembodiment, bulkier radicals are selected for R₁-R₆ to provideadditional spacing. Changing the electronic configuration or sterichindrances of R₅ and R₆ are particularly effective for modifying theorganometallic complex to provide greater dispersion. Suitable radicalsfor R₁-R₄ include methyl, benzene, or substituted benzene groups.Suitable bulky radicals for R₅ and R₆ include methyl, isopropyl,tert-butyl, benzene, or substituted benzene groups. R₅ and R₆ can besubstituted with Cl, Br, or other electron withdrawing groups to modifythe ligand electronic configuration.

B. Solid Support

The organometallic complexes are typically supported or formed on asolid support. The support may be organic or inorganic. It may bechemically inert, or it may serve a catalytic function complementary tothe catalyst complex.

One useful class of supports includes carbon-based materials, such ascarbon black, activated carbon, graphite, fluorinated carbon, and thelike. Other supports include polymers and other inorganic solids,metals, and metal alloys.

Another class of support materials includes porous, inorganic materials,such as alumina, silica, titania, kieselguhr, diatomaceous earth,bentonite, clay, zirconia, magnesia, metal oxides, zeolites, and calciumcarbonate.

The support may be in a variety of physical forms. It may be porous ornonporous. It may be a three-dimensional structure, such as a powder,granule, tablet, or extrudate. The support may be a two-dimensionalstructure such as a film, membrane, or coating. It may be aone-dimensional structure such as a narrow fiber. In the case where thesupport material is porous, it is preferable for the surface area to beat least 1 m²/g, more preferably greater than 20 m²/g.

In a preferred embodiment, the solid support has hydroxyl groups orother functional groups on its surface that would interact with thedelocalized electrons of the organometallic complex. This interactionbetween the support and the organometallic complex facilitatesdispersion of the complex on the support and can maintain the dispersednature of the metal atoms following manufacturing of the catalyst orduring use of the catalyst. It is also believed that bonding between thesupport and the organometallic complex can block access to the metalcenter on the side of the complex adjacent the support. This feature maybe partially responsible for the selectivity of the catalysts in someembodiments of the present invention.

C. Dispersing the Organometallic Complex

The organometallic complex is finely dispersed on the solid supportusing a solvent. Suitable solvents include any solvent that can dissolvethe organometallic complex, including toluene, xylene, chloroethanes,ethers such as diethyl ether, ketones, THF, dichloromethane, benzene,and the like. The solvent, solid support, and organometallic complex aremixed together to disperse the organometallic complex on the support.The mixing can occur in any order. However, the organometallic complexis typically first mixed with the solvent to form a solution orsuspension and then mixed with the support.

Dispersing the organometallic complex also includes drying or otherwiseremoving the solvent from the mixture to form an intermediate catalyst.In one embodiment, the solvent is removed using a rotary evaporator toevaporate the solvent.

The organometallic complex is dispersed on the solid support underconditions suitable to ensure that the complex is not destroyed (i.e.,the metal atoms remain complexed with the acetylacetonate derivedligands). For example, the temperature, pressure, and oxidative state ofthe complex can be controlled to prevent partial or complete removal ofthe ligands.

In an exemplary embodiment, the step of mixing the solvent, solidsupport, and organometallic complex is performed at standard temperatureand pressure. The drying or solvent removal step is also performed undernondestructive conditions. In a preferred embodiment, the solvent isremoved by heating at a temperature less than about 100° C. where oxygenis present, more preferably less than about 90° C. Where oxygen is notpresent, heating is preferably less than about 150° C. By ensuring thatthe organometallic complex is not destroyed during dispersion, the metalatoms can be evenly and finely dispersed on the support surface.

The organometallic complex can be loaded on the support within a widerange of loadings. The loading can range from about 0.01% to about 40%by weight of the supported catalyst particles, more preferably in arange of about 0.1% to about 25% by weight.

D. Activating the Intermediate Supported Catalyst

Once the catalyst is dispersed on the solid support material, thecatalyst is activating in a reduction step. In a preferred embodiment,the metal atoms of the organometallic complex are reduced usinghydrogen. Other suitable reducing agent include alcohols such asmethanol and phenol, aldehydes such as formaldehyde, ethylene glycol,hydrocarbons such as methane, ethylene, acetylene, propylene, and otherreagents that can be oxidized by the catalyst metals. The reduction stepis typically performed at temperatures between about 0° C. and about160° C.

It is believed that the organic ligand portions of the organometalliccomplexes at least partially remain complexed to the metal atoms evenafter activation; however, such binding is not required. By activatingthe intermediate catalyst after the organometallic complexes have beendispersed on the support surface, at least some of the advantages ofusing the organometallic complex can be realized.

II. Hydrogenation of Halonitro Aromatic Compounds

A. Preferred Halonitro Compounds

The catalyst of the present invention can selectively hydrogenate avariety of halonitro aromatic compounds. The aromatic compounds includecompounds having structures that follow the Hückels 4n+2 electron rule.For example, suitable aromatic compounds include benzenes, polycyclichydrocarbons (including partially hydrogenated polycyclic hydrocarbonssuch as tetralin), biphenyls, cyclopentadienyl anion andcycloheptatrienyl anion, anthraquinones, heteroaromatic substances suchas pyridines, pyrroles, azoles, diazines, triazines, triazoles, furans,thiophenes and oxazoles, condensated aromatic substances such asnaphthalene, anthracene, indoles, quinolines, isoquinolines, carbazoles,purines, phthalazines, benzotriazoles, benzofurans, cinnolines,quinazoles, acridines and benzothiophenes. The halogen and nitro groupsare preferably bound to carbon atoms of the aromatic nucleus.

The aromatic halonitro compounds also include one or more nitro groups,preferably one or two nitro groups. The aromatic halonitro compounds canalso include one or more halogen atoms, preferably one to three halogenatoms. The halogen atoms can be the same or different halogen atoms.Preferred halogens are chlorine and bromine.

The aromatic halonitro compounds may contain further substituents,preferably those without carbon/carbon and carbon/hetero atom multiplebonds.

The aromatic halonitro compounds most preferably correspond to thefollowing formula II:

wherein

-   R₁ signifies hydrogen, C₁-C₁₂-alkyl, C₁-C₁₂-halogen-alkyl,    C₆-C₁₆-halogen-aryl, C₃-C₆-halogen-heteroaryl, C₁-C₄-alkylphenyl,    C₁-C₄-alkoxyphenyl, halogen-C₁-C₄-alkylphenyl,    halogen-C₁-C₄-alkoxyphenyl, C₁-C₁₂-hydroxyalkyl, C₃-C₈-cycloalkyl,    C₃-C₈-cycloalkyl substituted by C₁-C₄-alkyl, C₆-C₁₆-aryl,    C₇-C₁₆-aralkyl, C₃-C₆-heterocycloalkyl, C₃-C₁₆-heteroaryl,    C₄-C₁₆-heteroaralkyl, SO₃ H, SO₂ R₂, SO₂ N(R₂)₂, or a group-Y₁ R₂;-   Y₁ signifies NR₂, oxygen or sulfur;-   R₂ signifies hydrogen, C₁-C₁₂-alkyl, C₁-C₁₂-halogen-alkyl,    C₆-C₁₆-halogen-aryl, C₃-C₁₆-halogen heteroaryl, C₁-C₄-alkylphenyl,    C₁-C₄-alkoxyphenyl, halogen-C₁-C₄-alkylphenyl,    halogen-C₁-C₄-alkoxyphenyl, C₁-C₁₂-hydroxyalkyl, C₃-C₈-cycloalkyl,    C₆-C₁₆-aryl, C₇-C₁₆-aralkyl, C₃-C₆-hetercycloalkyl,    C₃-C₁₆-heteroaryl, C₄-C₁₆-heteroaralkyl;-   X signifies fluorine, chlorine, bromine or iodine; and-   r,s, and t, independently of one another, signify a number 1, 2 or    3, whereby r+s+t is less than or equal to six. Preferably, r, s and    t, independent of one another, are 1 or 2.

In the above compounds, halogen is a fluorine, chlorine, bromine oriodine. Where there are several halogen substituents, these may be ofthe same type or mixed (for example Cl and F). Alkyl groups includemethyl, ethyl, isopropyl, n-propyl, n-butyl, iso-butyl, sec-butyl,tert-butyl, as well as the various isomeric pentyl, hexyl, heptyl,octyl, nonyl, decyl, undecyl, and dodecyl radicals.

Suitable halogen-alkyl groups includes, for example, fluoromethyl,difluoromethyl, trifluoromethyl, chloromethyl, dichloromethyl,trichloromethyl, 2,2,2-trifluoroethyl, 2-fluoroethyl, 2-chloroethyl and2,2,2-trichloroethyl; preferably trichloromethyl, difluorochloromethyl,trifluoromethyl and dichlorofluoromethyl.

Suitable alkoxy groups include, for example, methoxy, ethoxy, propoxy,1-propoxy, n-butoxy, i-butoxy, s-butoxy and t-butoxy; preferably methoxyand ethoxy.

Suitable halogen-alkoxy groups include, for example, fluoromethoxy,difluoromethoxy, trifluoromethoxy, 2,2,2-trifluoroethoxy,1,1,2,2-tetrafluoroethoxy, 2-fluoroethoxy, 2-chloroethoxy and2,2,2-trichloroethoxy; preferably difluoromethoxy, 2-chloroethoxy, andtrifluoromethoxy.

Suitable cycloalkyl and alkyl-substituted cycloalkyl groups include, forexample, cyclopropyl, dimethylcyclopropyl, cyclobutyl, cyclopentyl,methylcyclopentyl, cyclohexyl and cycloheptyl, but preferablycyclopropyl, cyclopentyl, and cyclohexyl.

Suitable alkoxyalkyl groups include, for example, methoxymethyl,ethoxymethyl, propoxymethyl, methoxyethyl, ethoxyethyl, propoxyethyl,methoxypropyl, ethoxypropyl, and propoxypropyl.

Phenyl groups can also be included as part of a substituent such asphenoxy, phenylthio, phenoxycarbonyl, phenylaminocarbonyl, benzyl orbenzoyl, and may in general be unsubstituted or substituted by furthersubstituents. These substituents can be in the ortho-, meta-, and/orpara-positions. Preferred substitution positions are the ortho- andpara-position to the ring attachment site. Preferred substituents arehalogen atoms.

Suitable aralkyl groups include, C₁-C₄-alkyl substituted with phenylgroups, including benzyl, phenethyl, 3-phenylpropyl, α-methylbenzyl,phenbutyl, and α,α-dimethylbenzyl.

Suitable aryl and analogous halogen-aryl groups include, for example,phenyl, tetralinyl, indenyl, naphthyl, azulenyl, and anthracenyl.

Suitable heteroaryl and analogous halogen-heteroaryl groups include, forexample, radicals of pyrrole, furan, thiophene, oxazole, thiazole,pyridine, pyrazine, pyrimidine, pyridazine, indole, purine, quinoline,and isoquinoline.

Heterocycloalkyl groups include, for example, radicals of oxirane,oxetane, azetidine, azirine, 1,2-oxathiolane, pyrazoline, pyrrolidine,piperidine, piperazine, morpholine, dioxolane, tetrahydropyran,tetrahydrofuran, and tetrahydrothiophene.

Examples of preferred halonitro aromatic substances are o-, m-, orp-nitrochlorobenzene; o-, m-, or p-nitrobromobenzene; o-, m-, orp-nitrofluorobenzene; 2-chloro-4-nitrotoluene, 2-bromo-4-nitrotoluene,4-chloro-2-nitrotoluene, 4-bromo-2-nitrotoluene,6-chloro-2-nitrotoluene, 3-chloro-4nitroethylbenzene, 2,5-, 2,3-, 2,4-,3,4-, or 3,5-dichloronitrobenzene, 3,4- or 2,4-dibromonitrobenzene,4-chloro-6-nitrometaxylene, 3-chloro-4-nitropropylbenzene,3-chloro-4-nitrobutylbenzene, 1-chloro-8-nitronaphthalene,1-chloro-2-nitronaphthalene, 1-nitro-5,8-dichloronaphthalene,3-chloro-4-fluoronitrobenzene, 2-fluoro-4-chloronitrobenzene,2,4-difluoronitrobenzene, 2,4,5-, 2,3,5-, or2,4,6-trichloronitrobenzene.

B. Hydrogenation Process

The reactions according to the invention are preferably carried out inthe liquid phase, especially with a powdered catalyst, eithercontinuously or discontinuously, as slurry phase hydrogenation or in abubble column or with a formed catalyst in a fixed bed. The reaction mayalso be carried out in the gas phase with a powdered catalyst in afluidized bed or with a formed catalyst in a fixed bed.

1. Solvents

If the halonitro compound to be hydrogenated is liquid at the reactiontemperature, hydrogenation may be carried out without solvents, or ifthe resulting amino compound is liquid under reaction conditions, thesemay serve as the solvent.

However, it is also possible to add inert solvents. Suitable solventsare for example water, alcohols such as methanol, ethanol, n-propanol,i-propanol, n-butanol, the isomeric butanols and cyclohexanol; ethers,esters and ketone, for example diethylether,methyl-tertiary-butyl-ether, tetrahydrofuran, dioxane, dimethoxyethane,acetic acid ethyl ester, acetic acid butyl ester, butyrolactone,acetone, methyl ethyl ketone, methyl-i-butyl ketone, or cyclohexanone,carboxylic acids such as acetic acid and propionic acid, dipolar-aproticsolvents such as dimethyl formamide, N-methylpyrrolidone, dimethylacetamide, sulpholane, dimethyl sulphoxide or acetonitrile, apolarsolvents such as toluene, xylene, or other aromatics, chlorinatedhydrocarbons such as methylene chloride or chloroethanes, C₃-C₇-alkanes,or cyclohexane.

These solvents may be used alone or as mixtures of at least twosolvents. In an especially preferred embodiment of the process accordingto the invention, the solvents employed are water, methanol, ethanol,iso-propanol, tetrahydrofuran, toluene, or xylene in pure form or asmixtures with the above-mentioned solvents, especially with alcoholsand/or C₁-C₄-carboxylic acids.

2. Reaction Conditions

The process according to the invention may be affected at a pressurebetween about 1 bar to about 100 bar, preferably at a pressure betweenabout 1 bar to about 40 bar, and most preferably at a pressure betweenabout 1 bar to about 20 bar.

The temperature maintained during the hydrogenation process can bebetween about 0° C. and about 160° C., preferably between about 20° C.and about 140° C., and most preferably between about 20° C. and about100° C.

The pH of the reaction mixture can be adjusted to desired value byadding bases or acids.

If solvents are used, the concentration of nitro aromatic substance inthe solution is preferably between about 5% and about 50% by weight,most preferably between about 10% and about 30% by weight.

The haloamino aromatic compounds manufactured using the process of thepresent invention have many uses. For example, some compounds areimportant chemical intermediates in the manufacture of dyes, pesticides,and pharmaceuticals.

III. EXAMPLES Example 1

Preparation of Platinum Acetylacetonate on Activate Carbon

6.0 g of activated carbon was soaked in 30 ml methanol for 12 h and thenfiltered. After filtration the carbon solid was dispersed in 60 mltoluene and a solution of 0.605 g platinum (II) acetylacetonate in 20 mltoluene. The total suspension was continually rotated on a rotaryevaporator for 12 h to evaporate the methanol and toluene. Theplatinum/carbon catalyst was dried in an oven at 80° C. for 6 h and thenactivated by reducing the catalyst under H₂ flow at 100° C. for 4 h.After cooling to room temperature, the catalyst, i.e., platinumacetylacetonate on activated carbon (Pt(acac)/C), was ready for use in ahydrogenation process. The resulting Pt(acac) catalyst had a weightcomposition of 5% Pt.

Example 2

General Selective Hydrogenation of 2-Chloro-Nitrobenzene

A typical hydrogenation procedure was conducted as follows: 4.04 g2-chloro-nitrobenzene catalyst and proper amount of catalystmanufactured in Example 1 was dispersed in 60 ml ethanol. Thissuspension was placed in a 300 ml stainless steel autoclave equippedwith a mechanical stir blade, a pressure gauge, a gas inlet tubeattached to a hydrogen source and a cooling circler connected to thetemperature controller. The autoclave was purged three times withnitrogen. After stabilizing the temperature at 25° C., the vessel waspressurized to 10.34 bar with hydrogen. The reaction mixture wasvigorously stirred and the reaction was stopped when no pressuredecrease was observed. The product was analyzed on gas chromatography(Agilent 6890 equipped with a FID detector and Rtx-5 Amine column). Thetest results for hydrogenation using the platinum acetylacetonatecatalyst manufactured according to the present invention are shown inTable 1 below and labeled “Pt(acac)/C”.

For comparison purposes, three commercially available catalysts weretested using the same hydrogenation procedure used with the Pt(acac)/Ccatalyst of the present invention. The three catalysts were obtainedfrom Degussa AG and are characterized by the following: (i) 5% Pt onactivated carbon, uniform, reduced, 50% wetted powder; (ii) 5% Pt onactivated carbon, eggshell, reduced, 50% wetted powder; (iii) 5% Pt onactivated carbon, Bismuth doped, 50% wetted powder. The test results forhydrogenation using commercially available catalyst (i)-(iii) are shownin Table 1 below. Reaction Reaction 2-chloro Temp. Pressure SM/C Timeaniline aniline Unknown Catalysts (° C.) (bar) ratio (h) (%) (%)intermediate (i) 25 10.34 5,000 10.25 76.05 15.61 8.34 (ii) 25 10.345,000 10.25 80.82 12.09 7.09 (iii) 25 10.34 5,000 20.5 90.73 0.47 8.80Pt(acac)₂/C 25 10.34 5,000 13.5 97.1 0.23 2.67

As shown in the foregoing test runs, hydrogenation of2-chloro-nitrobenzene using the catalyst of the present invention ishighly selective for 2-chloro aniline. The catalyst of the presentinvention produced only 0.23% of aniline and only 2.67% of other unknownintermediates. In some cases, this high selectivity using the catalystand methods of the present invention is sufficient to allow the productto be used without distillation, thereby significantly reducing the costof manufacturing the haloamine.

The present invention may be embodied in other specific forms withoutdeparting from its spirit or essential characteristics. The describedembodiments are to be considered in all respects only as illustrativeand not restrictive. The scope of the invention is, therefore, indicatedby the appended claims rather than by the foregoing description. Allchanges which come within the meaning and range of equivalency of theclaims are to be embraced within their scope.

1. A supported metal catalyst having high selectivity for hydrogenationof nitro groups of halonitro aromatic compounds manufactured accordingto a process comprising: dispersing an organometallic complex on a solidsupport to form an intermediate supported catalyst, wherein theorganometallic complex corresponds to formula I

wherein, R₁-R₆ comprise, independent of one another, one or more of anR, OR, OC(═O)R, or halide, wherein R stands for an alkyl, an aryl, or ahydrogen; Y₁-Y₄ are independently an O or S atom; and M is a metal atom;and reducing the metal atoms in order to activate the intermediatesupported catalyst, wherein after dispersing and prior to and duringactivation, the organometallic complex is not exposed to oxygen at atemperature greater than about 100° C.
 2. A supported metal catalyst asin claim 1, wherein prior to and during use, the supported metalcatalyst is not exposed to oxygen at a temperature greater than about100° C.
 3. A supported metal catalyst as in claim 1, wherein reducingthe metal atoms is performed by exposing the intermediate supportedcatalyst to hydrogen.
 4. A supported metal catalyst as in claim 1,wherein reducing the metal atoms is performed by exposing theintermediate supported catalyst to at least one of methanol, phenol, analdehyde, formaldehyde, ethylene glycol, methane, ethylene, acetylene,or propylene.
 5. A supported metal catalyst as in claim 1, whereinreducing the metal atoms is performed at a temperate less than about160° C. in a substantially oxygen free environment.
 6. A supported metalcatalyst as in claim 1, wherein the catalyst is dispersed on the supportusing a solvent.
 7. A supported metal catalyst as in claim 6, whereinthe solvent is selected from the group consisting of toluene, xylene,chloroethane, ethers, ketones, THF, dichloromethane, benzene, andmixtures thereof.
 8. A supported metal catalyst as in claim 1, wherein Mcomprises one or more platinum group metals.
 9. A supported metalcatalyst as in claim 8, wherein M comprises at least one member selectedfrom the group consisting of palladium, platinum, ruthenium, rhodium,and combinations thereof.
 10. A supported metal catalyst as in claim 1,wherein the solid support comprises hydroxyl groups on the surfacethereof that bond to at least a portion of organic ligands of theorganometallic complex.
 11. A supported metal catalyst as in claim 1,wherein the solid support comprises carbon.
 12. A supported metalcatalyst as in claim 11, wherein the solid support comprises at leastmember selected from the group consisting of carbon black, activatedcarbon, graphite, fluorinated carbon, and mixtures thereof.
 13. Asupported metal catalyst as in claim 1, wherein the solid supportcomprises at least member selected from the group consisting ofpolymers, inorganic solids, metals, metal alloys, and mixtures thereof.14. A supported metal catalyst as in claim 1, wherein the solid supportcomprises at least member selected from the group consisting of alumina,silica, titania, kieselguhr, diatomaceous earth, bentonite, clay,zirconia, magnesia, metal oxides, zeolites, calcium carbonate, andmixtures thereof.
 15. A supported metal catalyst as in claim 1, whereineach of R₁-R₄ is a CH₃ group and R₅ and R₆ are each a hydrogen.
 16. Asupported metal catalyst as in claim 1, wherein R₁-R₄ are independentlya methyl, benzene, or substituted benzene group.
 17. A supported metalcatalyst as in claim 1, wherein R₁-R₄ each comprise at least one carbonatom.
 18. A supported metal catalyst as in claim 1, wherein R₅ and R₆are independently a hydrogen, methyl, isopropyl, tert-butyl, benzene,substituted benzene, Cl, or Br group.
 19. A process for manufacturing anhaloamino aromatic compound comprising hydrogenating at least one nitrogroup of a halonitro aromatic compound in the presence of the catalystof claim
 1. 20. A process as in claim 19, wherein the halonitro aromaticcompound has the formula

wherein for the halonitro aromatic compound R₁ signifies hydrogen,C₁-C₁₂-alkyl, C₁-C₁₂-halogen-alkyl, C₆-C₁₆-halogen-aryl,C₃-C₆-halogen-heteroaryl, C₁-C₄-alkylphenyl, C₁-C₄-alkoxyphenyl,halogen-C₁-C₄-alkylphenyl, halogen-C₁-C₄-alkoxyphenyl,C₁-C₁₂-hydroxyalkyl, C₃-C₈-cycloalkyl, C₃-C₈-cycloalkyl substituted byC₁-C₄-alkyl, C₆-C₁₆-aryl, C₇-C₁₆-aralkyl, C₃-C₆-heterocycloalkyl,C₃-C₁₆-heteroaryl, C₄-C₁₆-heteroaralkyl, SO₃ H, SO₂ R₂, SO₂ N(R₂)₂, or agroup-Y₁ R₂; Y₁ signifies NR₂, oxygen or sulfur; R₂ signifies hydrogen,C₁-C₁₂-alkyl, C₁-C₁₂-halogen-alkyl, C₆-C₁₆-halogen-aryl, C₃-C₁₆-halogenheteroaryl, C₁-C₄-alkylphenyl, C₁-C₄-alkoxyphenyl,halogen-C₁-C₄-alkylphenyl, halogen-C₁-C₄-alkoxyphenyl,C₁-C₁₂-hydroxyalkyl, C₃-C₈-cycloalkyl, C₆-C₁₆-aryl, C₇-C₁₆-aralkyl,C₃-C₆-hetercycloalkyl, C₃-C₁₆-heteroaryl, or C₄-C₁₆-heteroaralkyl; Xsignifies fluorine, chlorine, bromine, or iodine; and r,s, and t,independent of one another, signify a number 1, 2, or 3, whereby r+s+tis less than or equal to six.
 21. A supported metal catalyst having highselectivity for hydrogenation of nitro groups of halonitro aromaticcompounds, comprising: a carbon support; and highly dispersed metal onthe carbon support, said highly dispersed being provided by: dispersingand then reducing an organometallic complex on a solid support, whereinthe organometallic complex initially corresponds to formula I prior toreducing

wherein, R₁-R₆ comprise, independent of one another, one or more of anR, OR, OC(═O)R, or halide, wherein R stands for an alkyl, an aryl, or ahydrogen; Y₁-Y₄ are independently an O or S atom; and M comprises ametal atom selected from the group consisting of palladium, platinum,ruthenium, rhodium, and mixtures thereof, wherein after dispersing priorto and during reducing, the organometallic complex is not exposed tooxygen at a temperature greater than about 100° C.
 22. A supported metalcatalyst as in claim 21, the reducing being performed at a temperatureless than about 90° C.
 23. A process for manufacturing an amino aromaticcompound, comprising: hydrogenating at least one nitro group of ahaloinitro aromatic compound in the presence of the catalyst accordingto claim 21, wherein the halonitro aromatic compound has the formula:

wherein, for the halonitro aromatic compound R₁ signifies hydrogen,C₁-C₁₂-alkyl, C₁-C₁₂-halogen-alkyl, C₆-C₁₆-halogen-aryl,C₃-C₆-halogen-heteroaryl, C₁-C₄-alkylphenyl, C₁-C₄-alkoxyphenyl,halogen-C₁-C₄-alkylphenyl, halogen-C₁-C₄-alkoxyphenyl,C₁-C₁₂-hydroxyalkyl, C₃-C₈-cycloalkyl, C₃-C₈-cycloalkyl substituted byC₁-C₄-alkyl, C₆-C₁₆-aryl, C₇-C₁₆-aralkyl, C₃-C₆-heterocycloalkyl,C₃-C₁₆-heteroaryl, C₄-C₁₆-heteroaralkyl, SO₃ H, SO₂ R₂, SO₂ N(R₂)₂, or agroup-Y₁ R₂; Y₁ signifies NR₂, oxygen, or sulfur; R₂ signifies hydrogen,C₁-C₁₂-alkyl, C₁-C₁₂-halogen-alkyl, C₆-C₁₆-halogen-aryl, C₃-C₁₆-halogenheteroaryl, C₁-C₄-alkylphenyl, C₁-C₄-alkoxyphenyl,halogen-C₁-C₄-alkylphenyl, halogen-C₁-C₄-alkoxyphenyl,C₁-C₁₂-hydroxyalkyl, C₃-C₈-cycloalkyl, C₆-C₁₆-aryl, C₇-C₁₆-aralkyl,C₃-C₆-hetercycloalkyl, C₃-C₁₆-heteroaryl, C₄-C₁₆-heteroaralkyl; Xsignifies fluorine, chlorine, bromine or iodine; and r,s, and t,independently of one another, signify a number 1, 2 or 3, whereby r+s+tis less than or equal to six.